If the PDF file fails to display all the page’s text, particularly multibyte characters such as Japanese or accented international characters, adjust your CSS to use a font that supports them. For example:
<apex:page showHeader="false" applyBodyTag="false" renderAs="pdf">
<head>
<style>
body { font-family: 'Arial Unicode MS'; }
</style>
</head>
<body>
これはサンプルページです。<br/>
This is a sample page: API version 28.0
</body>
</apex:page>
“Arial Unicode MS” is the only font supported for extended character sets that include multibyte characters.
Please also refer https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages/pages_output_pdf_considerations.htm
Best